Optical collimator-use lens component, optical collimator, and method of assembling these

ABSTRACT

Disclosed is an optical collimator-use lens component including: a thin tube; a partially spherical lens that has been fixed in an inner hole of the thin tube so that an insertion portion having a predetermined length is left, is made of glass whose refractive index is approximately uniform, and has translucent spherical surfaces, whose centers of curvature are approximately the same, at both ends of a cylindrical portion of the partially spherical lens; and an adhesive that bonds the partially spherical lens to the thin tube. An axial deviation amount between a center axis of the thin tube and an optical axis of the partially spherical lens is 5 μm or less. When a capillary tube, in whose inner hole an optical fiber has been fixed and whose axial deviation amount between an outer peripheral surface of the capillary tube and a core center of an end surface of the optical fiber is 1.5 μm or less, is inserted into the insertion portion of the thin tube and the end surface of the optical fiber is fixed at a position at which a distance of the end surface to a focal point position of the partially spherical lens becomes ±40 μm or less, emission light has an emission light bend of 0.2° or less with respect to the center axis of the thin tube.

BACKGROUND OF THE INVENTION

The present invention relates to an optical collimator-use lenscomponent, an optical collimator, a method of assembling the opticalcollimator-use lens component, and a method of assembling the opticalcollimator, with which an optical fiber for optical communications and alens are optically coupled to each other and emission light from theoptical fiber is converted into parallel light or parallel light iscondensed by the lens and is brought into incident on the optical fiber.

When a high-speed and large-capacity optical fiber communications systemis structured, many optical devices are used. The optical devicesinclude: an optical device that extracts an optical signal having anarbitrary wavelength from among multiple optical signals whosewavelengths have been multiplexed; and an optical device that uses anoptical crystal for matching phases of optical signals, and many opticalcollimators are used therein which each convert a widening opticalsignal emitted from an optical fiber into parallel light.

With a conventional optical collimator production method, as shown inFIG. 14, a capillary tube 3 with an optical fiber 2 is first fixed to athin tube 1, helium-neon laser light L generated by a visible rangelight source is caused to be emitted from the optical fiber 2, a lens 5held on a precision stage 4 is aligned so as to have an opticallyappropriate positional relation while the collimated state of the laserlight L is observed using a projection stage 6, and then the lens 5 isfastened to the thin tube 1 using an epoxy-based adhesive 7.

With the conventional assembling method described above, at the time ofassembling, the laser light L is actually caused to be emitted from theoptical fiber 2, so that it is required to connect the light source andthe optical fiber 2 with high precision at a several μm level. Therequirement leads to a problem in that preparation for production of theoptical collimator, such as work concerning the alignment and processingof the optical fiber 2, takes much time and labor and workability isextremely low.

Also, with the conventional assembling method, the actual holding marginof the lens 5 is less than several mm and the alignment of the opticalposition requires high precision at several μm or several tenths of μmlevel, so that there is a problem in that the workability is furtherlowered.

Further, at the time of the optical position alignment, a gap existsbetween the lens 5 and the thin tube 1, so that there occurs a problemin that when the adhesive 7 is cured for the fastening after thepositioning, the positions of the lens 5 and the like tend to bedisplaced due to volumetric shrinkage of the adhesive 7.

SUMMARY OF THE INVENTION

The present invention has an object to provide an optical collimator-uselens component, an optical collimator-use lens component assemblingmethod, an optical collimator, and an optical collimator assemblingmethod, with which the necessity of the conventional optical collimatorassembling method to pass light through an optical fiber at the time ofassembling is eliminated, the assembling is facilitated, and reliabilityconcerning optical alignment is increased.

In order to attain the object described above, according to the presentinvention, there is provided an optical collimator-use lens componentincluding: a thin tube; a partially spherical lens that has been fixedin an inner hole of the thin tube so that an insertion portion having apredetermined length is left, is made of glass whose refractive index isapproximately uniform, and has translucent spherical surfaces, whosecenters of curvature are approximately the same, at both ends of acylindrical portion of the partially spherical lens; and an adhesivethat bonds the partially spherical lens to the thin tube, in which anaxial deviation amount between a center axis of the thin tube and anoptical axis of the partially spherical lens is 5 μm or less, and when acapillary tube, in whose inner hole an optical fiber has been fixed andwhose axial deviation amount between an outer peripheral surface of thecapillary tube and a core center of an end surface of the optical fiberis 1.5 μm or less, is inserted into the insertion portion of the thintube and the end surface of the optical fiber is fixed at a position atwhich a distance of the end surface to a focal point position of thepartially spherical lens becomes ±40 μm or less, emission light has anemission light bend of 0.2° or less with respect to the center axis ofthe thin tube. According to the present invention, merely by insertingthe capillary tube, in whose inner hole the optical fiber has beenfixed, into the insertion portion of the thin tube and fixing thecapillary tube at a position at which a predetermined distance isobtained, it becomes possible to extremely easily produce an opticalcollimator, with which emission light has an emission light bend at alevel that has conventionally been impossible to realize.

When the axial deviation amount between the center axis of a thin tubeconstituting an optical collimator-use lens component and the opticalaxis of a partially spherical lens is 5 μm or less, as shown in FIG.1(A), it is possible to obtain a desired emission light bend θ ofemission light L that is 0.2° or less with respect to the center axis ofthe thin tube. On the other hand, when the axial deviation amountbetween the center axis of the thin tube and the optical axis of thepartially spherical lens exceeds 5 μm, as shown in FIG. 1(B), it becomesimpossible to obtain the desired emission light bend 9 of the emissionlight L that is 0.2° or less with respect to the center axis of the thintube.

It is important that the axial deviation amount between the outerperipheral surface of a capillary tube, in whose inner hole the opticalfiber 15 has been fixed, and the core center of an end surface of theoptical fiber 15 be 1.5 μm or less. When this axial deviation amountexceeds 1.5 μm, as shown in FIG. 1(B), it becomes impossible to realizethe desired emission light bend θ of the emission light that is 0.2° orless with respect to the center axis of the thin tube. In this case, thedistribution of beam intensity of the emission light L is decentered andit becomes impossible to obtain a desired coupling efficiency of anoptical signal.

Also, when a deviation occurs in coaxiality among a thin tube innersurface, the optical axis of the partially spherical lens, and theoptical axis of the optical fiber in the capillary tube, as shown inFIG. 1(B), an angle occurs in obtained parallel light. Although anallowable axial deviation amount is determined within an allowable anglerange in accordance with an application purpose, if this angle becomestoo large, attenuation of a light quantity occurs when the parallellight is further returned to an optical fiber by means of anotheroptical collimator. For instance, in the case of an optical collimatorthat uses a partially spherical lens made of LaSF015, which is a glassmaterial whose refractive index is around 1.8, and having a radius ofcurvature of 1.75 mm, in order to achieve an insertion loss (which is ageneral coupling characteristic) of 0.2 dB or less, it is required tosuppress the angle described above to around 0.1° or less. Also, in thiscase, an allowable axial deviation between the optical axis of thepartially spherical lens and the optical axis of the optical fiber 15becomes around 4 μm.

As to the thin tube used in the present invention, it is important thatthe inner surface of the thin tube and the optical axis of the partiallyspherical lens be arranged coaxially and the thin tube inner surface andthe capillary tube with the optical fiber have appropriate fittingdimensions so that when the capillary tube with the optical fiber isinserted into the thin tube inner surface, alignment is automaticallyperformed. When an excessive deviation occurs in the coaxiality amongthe thin tube inner surface, the optical axis of the partially sphericallens, and the optical fiber in the capillary tube, an angle occurs inobtained parallel light. Therefore, the allowable axial deviation amountof each element is determined by the allowable range of the angle inaccordance with an application purpose. Note that when the capillarytube with the optical fiber and the thin tube are fixed through welding,it is preferable that stainless steel that is superior in weldabilityand weatherability be used.

Also, as shown in FIG. 2, when an optical signal is given and receivedby arranging one pair of the optical collimators so as to oppose eachother, if the end surface of the optical fiber is arranged at a focalpoint position FP of the partially spherical lens, a beam waist BW ofthe emission light is formed at a position shown in FIG. 2(B). When theend surface of the optical fiber is arranged at a position displacedfrontward from the focal point position FP of the partially sphericallens, the beam waist BW of the emission light is formed at a positionshown in FIG. 2(C) (position close to the partially spherical lens). Inthis case, when the end surface of the optical fiber is arranged at aposition displaced frontward by 40 μm or more from the focal pointposition FP of the partially spherical lens, the beam waist BW is notformed and the emission light widens. On the other hand, when the endsurface of the optical fiber is arranged at a position displacedbackward from the focal point position FP of the partially sphericallens, the beam waist BW of the emission light is formed at a positionshown in FIG. 2(D) (position away from the partially spherical lens). Inthis case, when the end surface of the optical fiber is arranged at aposition displaced backward by 40 μm or more from the focal pointposition FP of the partially spherical lens, the beam waist BW is notformed and the emission light widens. Accordingly, it is important thatthe end surface of the optical fiber be fixed at a position at which itsdistance from the focal point position of the partially spherical lensis ±40 μm or less.

Any partially spherical lens is usable as the partially spherical lensused in the present invention so long as it is made of optical glass orthe like, whose refractive index is approximately uniform, and has beenformed using a material with which it is possible to produce a partiallyspherical lens having high focal point accuracy through working into aperfectly spherical shape; a partially spherical lens produced bygrinding a periphery of a sphere lens having high sphericity is suitedfrom the viewpoint of reduction in size and diameter of the opticalcollimator. Note that the optical axis of the partially spherical lensbecomes an axis that passes through the center of curvature of the lensand is parallel to the center axis of the thin tube, so that noinfluence is exerted by aside surface shape, inclination of a workingaxis, an axial deviation, and the like at the time of grinding of theperiphery. Also, it is preferable that optical glass, such as BK7, K3,TaF3, LaF01, or LaSF015, be used to produce the partially sphericallens.

The partially spherical lens is a lens that originally has sphericalaberration and when its refractive index is low, the sphericalaberration becomes large and the partially spherical lens lowers thecoupling efficiency of an optical signal emitted from an optical fiberend surface or an optical signal condensed on an optical fiber endsurface. Accordingly, it is preferable that the partially spherical lensused in the present invention be 1.7 or more in refractive index. Withthis construction, it becomes possible to produce easily an opticalcollimator, with which it is possible to obtain parallel light havinghigh connection efficiency and an emission light bend.

In the construction described above, it is preferable that the distancebetween the end surface of the optical fiber and the translucentspherical surface of the partially spherical lens, that is, a distancewhere the radius of curvature R of the translucent spherical surface issubtracted from the focal distance f of the partially spherical lens be0.1 mm or more, more preferably 0.15 mm or more. With this construction,it becomes possible to significantly reduce light that is reflected fromthe translucent spherical surface of the partially spherical lens and isincident on the optical fiber. As a result, variations of optical signalcharacteristics are suppressed within a working distance and it becomespossible to structure a high-speed and large-capacity opticalcommunications system with the partially spherical lens.

When the radius of curvature R of the partially spherical lens is small,for instance, if the distance between the end surface 15 a of theoptical fiber 15 and the translucent spherical surface of the partiallyspherical lens 12 is less than 0.1 mm, as shown in FIG. 3, a largequantity of reflection light Lb from the translucent spherical surfacereturns to the end surface 15 a of the optical fiber 15 and becomesnoise. On the other hand, when the distance becomes longer than “focalpoint position+40 μm”, no beam waist BW is formed and the light widens.Therefore, it is important that the distance between the end surface ofthe optical fiber and the translucent spherical surface of the partiallyspherical lens be 0.1 mm or more. Also, in order to further reduce thereflection light that is incident again on the optical fiber endsurface, the distance is preferably 0.15 mm or more.

In the construction described above, in order to make it possible toobserve the distance between the end surface of the optical fiber andthe translucent spherical surface of the partially spherical lens fromthe outside, a through portion may be provided at a predeterminedposition of the thin tube.

In order to make it possible to observe the distance between the endsurface of the optical fiber and the translucent spherical surface ofthe partially spherical lens from the outside, a metal-made sleeveprovided with an observation window as the through portion at thepredetermined position may be used, for instance. In order to obtainparallel light, it is required to arrange the optical fiber end surfaceat the focal point position of the partially spherical lens. In thepresent invention, such a thin tube having a through portion is used, sothat it is possible to adjust the distance between the vertex of thetranslucent spherical surface of the partially spherical lens and theoptical fiber end surface with ease by measuring the distance using ameasuring machine such as a laser light length measuring machine or amicroscope. Also, after the adjustment of the distance described aboveis performed, the capillary tube with the optical fiber is fixed in thethin tube using an adhesive or through welding. When doing so, it ispossible to observe a gap portion between the end surface of the opticalfiber and the translucent spherical surface of the partially sphericallens, so that this construction is also suited for confirmation ofwhether any problems occur in a light passing region.

Alternatively, in the construction described above, the thin tube may beformed using a transparent body with which measurement of the distancebetween the end surface of the optical fiber and the translucentspherical surface of the partially spherical lens is possible from theoutside. With this construction, it becomes possible to produce the sameeffect as above.

For instance, it is possible to use as the thin tube a transparent glasstube that transmits light or magnetism for the measurement of thedistance described above. As to the material of the thin tube, when thethin tube is used as a tube, borosilicate glass or the like is suitedwhich has favorable thermal workability, transmits light and magnetism,and is superior in weatherability.

In the construction described above, the thin tube may be formed usingglass or crystallized glass. With this construction, it becomes possibleto use a thin tube that is high in accuracy and is low in cost. As aresult, it becomes possible to reduce the structuring cost of ahigh-speed and large-capacity optical communications system.

Any glass-made or crystallized-glass-made thin tube is usable so long asit has a coefficient of thermal expansion that is close to those of thepartially spherical lens and the capillary tube. When the thin tube ismade of a material with which it is possible to control the state ofcrystal precipitation, it becomes possible to obtain the thin tube withhigh accuracy and at low cost using a continuous molding method.

In the construction described above, the thin tube may be a splitsleeve.

As to the inner diameter size of the split sleeve, it is important thatfitting with the capillary tube with the optical fiber have a tight fitrelation. A difference in size between them exerts an influence on adeviation between the inner surface of the thin tube and the opticalaxis of the partially spherical lens. When the split sleeve has an innerdiameter that is smaller than the capillary tube with the optical fiberby several μm, it becomes possible to eliminate the size difference, sothat this construction is effective. It is possible to use as the splitsleeve a split sleeve made of a metal, zirconia ceramics, or the like.

When the split sleeve is made of a metal, it is preferable that ametallic material be used which is low in hardness because it becomespossible to prevent damage to the surfaces of the partially sphericallens and the capillary tube with the optical fiber and to preventdusting. Phosphor bronze, stainless steel, or the like that is high indimensional reproducibility is suited as such a metallic material.

In the construction described above, an epoxy-based resin or a lowmelting point glass frit may be used as the adhesive, which has beenmixed with a filler made of at least one material selected from thegroup consisting of ceramics, glass, and metals.

In the case of an epoxy adhesive that is generally used to assemble acollimator, volumetric shrinkage of around 20% occurs at the time ofcuring. In order to prevent a positional displacement of the partiallyspherical lens due to such shrinkage, it is effective that the adhesivebe mixed with a filler made of at least one material selected from thegroup consisting of ceramics, glass, and metals. Also, when the adhesiveis mixed with the filler, a thixotropic property is imparted to theadhesive, so that this construction is also effective at preventingliquid dropping and improving the strength of the adhesive.

Also, the following construction may be adopted. An inner thin tubehaving an inner hole with a predetermined inner diameter is insertedinto and arranged in the insertion portion of the thin tube. The innertube is bonded to and fixed in the insertion portion under a state wherean end surface of the inner thin tube that is at right angles to thetube axis of the inner thin tube with predetermined accuracy is abuttedagainst the translucent spherical surface of the partially sphericallens. With this construction, it becomes possible to fasten thepartially spherical lens and the inner thin tube at precise positpositions with respect to the thin tube so as to have a precise coaxialrelation. As a result, it becomes possible to produce an opticalcollimator that is superior in optical characteristics.

It is preferable that the inner thin tube used in the present inventionhave an outer diameter with which fitting into the insertion portion ofthe thin tube has a clearance fit relation with a clearance of severalμm or less or a tight fit relation, have an inner diameter that islarger than the capillary tube by several μm so that emission/incidentlight from/onto the optical fiber will never be intercepted, and includean end surface that is at right angles to the tube axis of the innerthin tube with predetermined accuracy at a level of from several □ toseveral □.

In the construction described above, the thin tube and/or the inner thintube may be formed using transparent glass that transmits 50% or more oflight, whose wavelength is 350 to 500 nm, with a thickness of 1 mm. Withthis construction, it becomes possible to fasten the optical fiber orthe capillary tube with the optical fiber in the inner thin tube in ashort time using a light curing adhesive. As a result, it becomespossible to produce the optical collimator with efficiency.

Here, the transmission of 50% or more of light, whose wavelength is 350to 500 nm, with the thickness of 1 mm means that light in the range offrom near ultraviolet rays to blue visible rays, against which the lightcuring adhesive exhibits high curing reaction sensitivity, issufficiently transmitted. It is possible to use as the transparent glassborosilicate glass, quartz glass, or the like where the impurity contentof iron or the like that lowers transparency has been suppressed.

Also, in order to attain the object described above, the presentinvention provides a method of assembling an optical collimator-use lenscomponent including: a thin tube; a partially spherical lens that hasbeen fixed in an inner hole of the thin tube so that an insertionportion having a predetermined length is left, is made of glass whoserefractive index is approximately uniform, and has translucent sphericalsurfaces, whose centers of curvature are approximately the same, at bothends of its cylindrical portion; and an adhesive that bonds thepartially spherical lens to the thin tube, the optical collimator-uselens component assembling method including: inserting an inner thin tubehaving an inner hole with a predetermined inner diameter into the innerhole of the thin tube; fixing the inner thin tube under a state where anend surface of the inner thin tube that is at right angles to a tubeaxis of the inner thin tube with predetermined accuracy exists at apredetermined position; positioning the partially spherical lens byinserting the partially spherical lens into the inner hole of the thintube so as to be abutted against the end surface of the inner thin tube;and bonding and fixing the partially spherical lens in the thin tube.With this method according to the present invention, it becomes possibleto perform the positioning of the partially spherical lens with respectto the inner hole of the thin tube with accuracy. As a result, itbecomes possible to produce the optical collimator-use lens componentwith efficiency.

With the assembling method according to the present invention, in orderto perform the positioning of the partially spherical lens withaccuracy, it is important that the inserted inner thin tube have thethin tube has a clearance fit relation with a clearance of several μm orless or a tight fit relation, and the end surface of the inner thin tubethat is at right angles to the tube axis of the inner thin tube withpredetermined accuracy be positioned at a predetermined position. Notethat the thin tube is given an extra length with which when thecapillary tube with the optical fiber is arranged so that its distanceto the partially spherical lens becomes appropriate, it is possible tohold the capillary tube with sufficient strength. Also, when apositional displacement at the time of curing of the adhesive causes nooptical problem, an adhesive not mixed with a filler may be used.

In the construction described above, before or after the partiallyspherical lens is bonded and fixed in the thin tube, the inner thin tubemay be removed from the inside of the thin tube. With this construction,it becomes possible to achieve highly accurate coaxiality between thethin tube inner hole and the partially spherical lens with ease. As aresult, it becomes possible to produce an optical collimator-use lenscomponent, which is superior in optical characteristics, with highreproducibility as well as with ease.

For instance, it is possible to realize highly accurate coaxialitybetween the thin tube inner hole and the center of curvature (that is,the optical axis) of the partially spherical lens with ease by:adsorbing the partially spherical lens to the inner thin tube having anouter diameter, which is the same as that of the capillary tube with theoptical fiber, and a hole that is coaxial with the outer diameter;inserting the partially spherical lens into the thin tube; fastening thepartially spherical lens by filling a gap between the partiallyspherical lens and the thin tube with an adhesive and curing theadhesive; and then stopping the adsorption and pulling out the innerthin tube.

In the optical collimator-use lens component according to the presentinvention, the thin tube inner surface and the optical axis of thepartially spherical lens are arranged coaxially and the thin tube innersurface and the capillary tube with the optical fiber are set atappropriate fitting dimensions so that alignment is performedautomatically when the capillary tube with the optical fiber is insertedinto the thin tube inner surface. Here, if a deviation occurs in thecoaxiality among the thin tube inner surface, the optical axis of thepartially spherical lens, and the optical fiber in the capillary tube,an angle occurs in obtained parallel light. Therefore, an allowableaxial deviation amount is determined within an allowable range of theangle in accordance with an application purpose. Also, aside from thisconstruction, the same effect may be produced using a spacer, whichadjusts the distance between the vertex of the partially spherical lensand the optical fiber end surface, or a protrusion-like stopper providedon the thin tube inner surface.

Further, in order to attain the object described above, according to thepresent invention, there is provided an optical collimator including alens component and a capillary tube into whose inner hole an opticalfiber has been fixed, in which the lens component includes: a thin tube;a partially spherical lens that has been fixed in an inner hole of thethin tube so that an insertion portion having a predetermined length isleft, is made of glass whose refractive index is approximately uniform,and has translucent spherical surfaces, whose centers of curvature areapproximately the same, at both ends of a cylindrical portion of thepartially spherical lens; and an adhesive that bonds the partiallyspherical lens to the thin tube, an axial deviation amount between acenter axis of the thin tube and an optical axis of the partiallyspherical lens being 5 μm or less, an axial deviation amount between anouter peripheral surface of the capillary tube and a core center of anend surface of the optical fiber is 1.5 μm or less, and the capillarytube is inserted into the insertion portion of the thin tube of the lenscomponent and is fixed at a position at which a distance of the endsurface of the optical fiber to a focal point position of the partiallyspherical lens becomes ±40 μm or less.

As to each construction element of the optical collimator describedabove, every point already described in connection with the opticalcollimator-use lens component applies, so that the following descriptionwill be simplified by omitting repetitive description.

Also, in the optical collimator according to the present invention, forthe same reason as that already described in connection with the opticalcollimator-use lens component, it is possible to adopt each constructiondescribed below.

(1) The partially spherical lens is 1.7 or more in refractive index.

(2) The distance between the end surface of the optical fiber and thetranslucent spherical surface of the partially spherical lens is 0.1 mmor more.

(3) A material of the thin tube is glass or crystallized glass.

(4) The thin tube is a split sleeve.

(5) A material of the split sleeve is a metal.

(6) The adhesive is an epoxy-based resin or a low melting point glassfrit mixed with a filler made of at least one material selected from thegroup consisting of ceramics, glass, and metals.

(7) An inner thin tube having an inner hole with a predetermined innerdiameter is inserted into and arranged in the insertion portion of thethin tube, and is bonded and fixed in the insertion portion under astate where an end surface of the inner thin tube that is at rightangles to a tube axis of the inner thin tube with predetermined accuracyis abutted against the translucent spherical surface of the partiallyspherical lens.

Further, a construction may be employed in which the distance betweenthe end surface of the optical fiber and the translucent sphericalsurface of the partially spherical lens is reduced from an optimum valuecalculated from the refractive index of the partially spherical lens anda spherical radius of the translucent spherical surface and is set sothat a beam waist position falls within the range of a predeterminedvalue ±5 mm within a substantially required working distance.

When the beam waist position of a collimated beam of emission light fromthe optical collimator falls outside the range of a predetermined value±5 mm, coupling efficiency is lowered due to light wave characteristics.By adopting the construction described above, it becomes possible totransmit the emitted collimated beam to an optical fiber on a lightreception side with high coupling efficiency. As a result, it becomespossible to maintain high-quality communication performance.

Further, in order to attain the object described above, according to thepresent invention, there is provided a method of assembling an opticalcollimator including a lens component and a capillary tube into whoseinner hole an optical fiber has been fixed, the lens componentincluding: a thin tube; a partially spherical lens that has been fixedin an inner hole of the thin tube so that an insertion portion having apredetermined length is left, is made of glass whose refractive index isapproximately uniform, and has translucent spherical surfaces, whosecenters of curvature are approximately the same, at both ends of acylindrical portion of the partially spherical lens; and an adhesivethat bonds the partially spherical lens to the thin tube, an axialdeviation amount between a center axis of the thin tube and an opticalaxis of the partially spherical lens being 5 μm or less, an axialdeviation amount between an outer peripheral surface of the capillarytube and a core center of an end surface of the optical fiber being 1.5μm or less, and the capillary tube being inserted into the insertionportion of the thin tube of the lens component and being fixed at aposition at which a distance of the end surface of the optical fiber toa focal point position of the partially spherical lens becomes ±40 μm orless, the optical collimator assembling method including: positioning,at the time of the fixation at the position, the capillary tube bymeasuring a distance between the end surface of the optical fiber andthe translucent spherical surface of the partially spherical lens fromthe outside.

As to each construction element in the optical collimator assemblingmethod described above, every point already described in connection withthe optical collimator-use lens component assembling method applies, sothat the following description will be simplified by omitting repetitivedescription.

Also, in the optical collimator assembling method according to thepresent invention, for the same reason as that already described inconnection with the optical collimator-use lens component assemblingmethod, it is possible to adopt each construction described below.

(1) The thin tube has a through portion at a predetermined position withwhich the distance between the end surface of the optical fiber and thetranslucent spherical surface of the partially spherical lens can beobserved from the outside, and the positioning is performed while thedistance between the spherical surface of the partially spherical lensand the end surface of the optical fiber is measured from the outside.

(2) The thin tube is formed using a transparent body with which thedistance between the end surface of the optical fiber and thetranslucent spherical surface of the partially spherical lens can bemeasured from the outside, and the positioning is performed while thedistance between the end surface of the optical fiber and thetranslucent spherical surface of the partially spherical lens ismeasured from the outside.

(3) At least one of the thin tube and the inner thin tube is made oftransparent glass that transmits 50% or more of light, whose wavelengthis 350 to 500 nm, with a thickness of 1 mm.

Further, the distance between the end surface of the optical fiber andthe translucent spherical surface of the partially spherical lens may bereduced from an optimum value calculated from the refractive index ofthe partially spherical lens and a spherical radius of the translucentspherical surface and may be set so that a beam waist position fallswithin the range of a predetermined value ±5 mm within a substantiallyrequired working distance. With this construction, it becomes possibleto transmit a collimated beam of emission light with high couplingefficiency. As a result, it becomes possible to maintain high-qualitycommunication performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 are explanatory diagrams of a bend of emission light emitted froman optical collimator, in which FIG. 1(A) shows an emission light bendin the case where an optical collimator-use lens component according tothe present invention is used, and FIG. 1(B) shows an emission lightbend in the case where a faulty optical collimator is used;

FIG. 2(A) shows a state where optical collimators are arranged so as tooppose each other, FIG. 2(B) shows a beam waist position in the casewhere an optical fiber end surface is arranged at a focal point positionof a partially spherical lens, FIG. 2(C) shows a beam waist position inthe case where the optical fiber end surface is arranged frontward withrespect to the focal point position of the partially spherical lens, andFIG. 2(D) shows a beam waist position in the case where the opticalfiber end surface is arranged backward with respect to the focal pointposition of the partially spherical lens;

FIG. 3 shows a relation between (i) a distance from a spherical surfaceand the radius of curvature of the partially spherical lens to theoptical fiber end surface and (ii) reflection light;

FIG. 4 show optical collimator-use lens components, in which FIG. 4(A)is a plan view and FIG. 4(B) is a cross-sectional view;

FIG. 5 show optical collimators, in which FIG. 5(A) is a plan view andFIG. 5(B) is a cross-sectional view;

FIG. 6 is a cross-sectional view showing the main portion of the opticalcollimator;

FIG. 7 show a method of using the optical collimator, in which FIG. 7(A)shows a state where offset positions are misaligned, FIG. 7(B) shows astate where the offset positions are aligned, and FIG. 7(C) shows astate where a position of emission light is aligned under a state wherethe offset positions are misaligned;

FIGS. 8(A) and (B) show a split sleeve, FIG. 8(C) shows an inner thintube, FIG. 8(D) shows a partially spherical lens, and FIG. 8(E) shows acapillary tube with an optical fiber;

FIG. 9 show assembling steps of the optical collimator-use lenscomponent and the optical collimator, in which FIG. 9(A) shows a step inwhich the inner thin tube is fitted into the split sleeve, FIG. 9(B)shows a step in which the partially spherical lens is fitted into thesplit sleeve, FIG. 9(C) shows a step in which the inner thin tube isremoved from the split sleeve, and FIG. 9(D) shows a step in which thecapillary tube with the optical fiber is fitted into the split sleeve;

FIG. 10 is a cross-sectional view of an optical collimator-use lenscomponent according to another embodiment;

FIG. 11 is a cross-sectional view of an optical collimator according tothe other embodiment;

FIG. 12 (A) shows a glass thin tube, FIG. 12 (B) shows a glass innerthin tube, FIG. 12 (C) shows a partially spherical lens, and FIG. 12 (D)shows a capillary;

FIG. 13 show assembling steps of the optical collimator-use lenscomponent and the optical collimator, in which FIG. 13(A) shows theglass thin tube, FIG. 13(B) shows a step in which the glass inner thintube is fitted into the glass thin tube, FIG. 13(C) shows a step inwhich the partially spherical lens is fitted into the glass thin tube,and FIG. 13(D) shows a step in which a capillary tube with an opticalfiber is fitted into the glass inner thin tube; and

FIG. 14 is an explanatory diagram of a conventional optical collimatorassembling method.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention will now be described withreference to the accompanying drawings.

As shown in FIG. 4, an optical collimator-use lens component 10 in thisembodiment includes: a phosphor-bronze-made or stainless-made splitsleeve 11 that has a linear split portion 11 b and a through portion 11c, is 1.60 mm in outer diameter, is 1.249 mm in inner diameter of itsinner hole 11 d, and is 5.5 mm in total length; a partially sphericallens 12 fixed in the inner hole 11 d of the split sleeve 11 so that aninsertion portion 11 a having a length of 2.5 mm is left; and anadhesive 13 made of an epoxy-based resin for bonding the partiallyspherical lens 12 to the split sleeve 11. The partially spherical lens12 is made of optical glass LaSF015, whose refractive index isapproximately uniform, and has translucent spherical surfaces 12 b and12 c, whose centers of curvature R are approximately the same andradiuses of curvature are each 1.500 ±0.002 mm, at both ends of itscylindrical portion 12 a. The axial deviation amount between the centeraxis of the split sleeve 11 and the optical axis of the partiallyspherical lens 12 is 3 μm. Also, an antireflection film is formed foreach of the translucent spherical surfaces 12 b and 12 c of thepartially spherical lens 12.

FIG. 5 show an optical collimator 30 in this embodiment that uses theoptical collimator-use lens component 10. A capillary tube 14, in whoseinner hole 14 b a single-mode optical fiber 15 has been fixed, isinserted into and fixed in the insertion portion 11 a of the splitsleeve 11. The capillary tube 14 is 1.249 mm±0.5 μm in outer diameterand is 5.0 mm in total length. Also, the axial deviation amount betweenan outer peripheral surface 14 a of the capillary tube 14 and the corecenter of an end surface 15 a of the optical fiber 15 is 0.5 μm. The endsurface 15 a of the optical fiber 15 is inclined by 8° with respect to aplane vertical to the optical axis of the optical fiber 15 and anantireflection film is formed for the end surface 15 a. When thecapillary tube 14 is fixed at a position at which a distance d1 betweenthe end surface 15 a of the optical fiber 15 and the spherical surface12 b of the partially spherical lens 12 becomes 0.215 mm±3 μm, emissionlight has an emission light bend of 0.1° that is within a desired rangeof 0.2° or less.

As shown in FIG. 6, in the optical collimator 30 where the capillarytube 14 has been fixed to the optical collimator-use lens component 10,when an optical signal inclined by β with respect to the optical axis isbrought into incident on the partially spherical lens 12 from the endsurface 15 a of the optical fiber 15 inclined by an inclination angle αwith respect to the plane vertical to the optical axis, an offset Woccurs between the optical axis of the optical fiber 15 and the opticalaxis of emission light from the partially spherical lens 12. This offsetW has a relation shown in the figure due to the refractive index n3 andthe radius of curvature e partially spherical lens 12 and theinclination angle α of the end surface 15 a of the optical fiber 15.

Next, four optical collimators 30 were produced and insertion loss andreturn loss measurement was performed.

As shown in FIG. 7, in the optical collimator 30 produced by fixing thecapillary tube 14, to which the optical fiber 15 having the inclined endsurface 15 a has been fastened, to the optical collimator-use lenscomponent 10, an offset W of only 114 μm occurs between the emissionlight from the partially spherical lens 12 and the optical axis of theoptical fiber 15. Therefore, when the directions of offsets W do notcoincide with each other, an axial deviation loss of an optical signalshown in FIG. 7(A) occurs. In view of this problem, at the time of theinsertion loss and return loss measurement, a working distance was setat 20 mm and the offset positions of one pair of the opticalcollimator-use lens components 10 arranged so as to oppose each otherwere aligned as shown in FIG. 7(B) or 7(C). Table 1 below shows a resultof the insertion loss measurement.

TABLE 1 Minimum value Maximum value Mean Measurement No. dB dB value dB1 0.143 0.151 0.147 2 0.118 0.126 0.122 3 0.093 0.101 0.097 4 0.1060.114 0.110 5 0.143 0.151 0.147 6 0.143 0.151 0.147 Minimum value dB0.093 Maximum value dB 0.151 Mean value dB 0.128 Standard deviation dB0.021

Also, the return loss of the optical collimator 30 described above wasmeasured. Table 2 below shows a result of this measurement.

TABLE 2 Return loss (dB) Eccentricity −5 μm Design distance +5 μm A 5.062.32 62.44 62.60 A 4.0 61.52 61.99 62.54 B 4.5 61.88 61.99 62.22 C 2.561.91 62.05 62.30 Mean value 61.91 62.12 62.42 Return loss Unfavorable<-> Favorable

The measurements shown in Table 2 reveal that as a distance between thepartially spherical lens and the optical fiber is decreased, the returnloss is increased. When the distance described above is 0.215±5 μm, thereturn loss changes by around ±0.3 dB. Also, a relation between theeccentricity of the partially spherical lens with respect to the sleeveand the return loss was determined to show that when the amount of theeccentricity is 5 μm or less, the return loss changes by around 0.5 dB.Further, measurement as to a relation between the eccentricity of thepartially spherical lens with respect to the sleeve and the insertionloss was performed. The dependency of the insertion loss on theeccentricity was confirmed by fixing the optical collimator on a lightsource side as a reference optical collimator and decentering the lensof the optical collimator on a light reception side by 4 to 5 μm in eachof a 0° direction, a 90° direction, a 180° direction, and a 270°direction. Table 3 below shows a result of this measurement.

TABLE 3 Dependency of Insertion Loss on Eccentricity Direction Insertionloss (dB) 1  0° 0.13 2  90° 0.12 3 180° 0.13 4 270° 0.13

The measurements shown in Table 3 show that, as to the relation betweenthe eccentricity of the partially spherical lens with respect to thesleeve and the insertion loss, the changing amount of the insertion lossin relation to the direction of the eccentricity is around 0.01 dB.

Also, as to the relation between the direction of the eccentricity andthe return loss, measurement was performed using a partially sphericallens having an amount of eccentricity of 4.5 μm. Table 4 below shows aresult of this measurement. Note that in Table 4, a case is shown inwhich a direction (1) of eccentricity is set as a direction in which thetip end of the optical fiber gets closer to the optical axis of thepartially spherical lens, and a direction (2) of eccentricity is set asa direction in which the tip end of the optical fiber gets away from theoptical axis of the partially spherical lens.

TABLE 4 Return loss (dB) Direction (1) of Direction (2) of MeasurementNo. eccentricity eccentricity 1 62.43 61.54 2 62.50 61.57 3 62.12 61.904 61.45 60.75 5 63.68 61.98 Mean value 62.44 61.55 Favorable <->Unfavorable

The measurements shown in Table 4 reveal that the direction (1) ofeccentricity is better than the direction (2) of eccentricity. Asdescribed above, when the amount of the eccentricity is managed so as tobecome 5 μm or less, the changing amount of the return loss becomesaround 0.5 dB.

Next, a method of assembling the optical collimator-use lens component10 and a method of assembling the optical collimator 30 will bedescribed.

First, as shown in FIGS. 8(A) and (B), the split sleeve 11 is producedby establishing the through portion 11 c in a split sleeve that has alinear split portion, is 1.60 mm in outer diameter, is 1.249 mm in innerdiameter of its inner hole, and is 5.5 mm in total length. When doingso, working is performed while attention is paid so that the accuracy ofthe split sleeve 11 is not lowered.

Next, as shown in FIG. 8(C), an inner thin tube 17 is produced which is1.249 mm in outer diameter, is 0.68 mm in inner diameter of its innerhole 17 b, and has an end surface 17 a that is at right angles to itstube axis with accuracy of ±0.1° or less.

Then, as shown in FIG. 8(D), a sphere lens, whose radius of curvature Ris 1.500±0.002 mm, is produced using optical glass LaSF015 whoserefractive index is approximately uniform. Next, the cylindrical portion12 a is formed by grinding this sphere lens while rotating the lensabout its optical axis. Following this, a ring-like groove 12 d isformed into which the adhesive is to be charged. In this manner, thepartially spherical lens 12 having the translucent spherical surfaces 12b and 12 c on its both ends is obtained.

Next, as shown in FIG. 8(E), the capillary tube 14 is produced which is1.249 mm±0.5 μm in outer diameter and is 5.0 mm in total length, and theoptical fiber 15 is fixed in the inner hole 14 b. The end surface 15 aof the optical fiber 15 is inclined by 8° with respect to a planevertical to the optical axis of the optical fiber 15 and anantireflection film is formed for the end surface 15 a. The axialdeviation amount between the outer peripheral surface 14 a of thecapillary tube 14 and the core center of the end surface 15 a of theoptical fiber 15 is 0.5 μm.

Next, as shown in FIG. 9(A), the inner thin tube 17 is inserted into theinner hole 11 d of the split sleeve 11 and is fixed at a position atwhich a distance between its right-angled end surface 17 a and the endsurface of the split sleeve 11 becomes 2.5 mm. Then, as shown in FIG.9(B), the partially spherical lens 12 is inserted into the inner hole 11d of the split sleeve 11 and the translucent spherical surface 12 b isabutted against the end surface 17 a of the inner thin tube 17, therebypositioning the partially spherical lens 12. Following this, as shown inFIG. 9(C), the partially spherical lens 12 is fastened to the inner hole11 d of the split sleeve 11 using the adhesive 13. After the adhesive 13is completely cured, the inner thin tube 17 is removed to provide theoptical collimator-use lens component 10.

Then, as shown in FIG. 9(D), the capillary tube 14, in whose inner hole14 b the optical fiber 15 has been fixed, is inserted into the insertionportion 11 a of the split sleeve 11. Then, while observation/measurementthrough the through portion 11 c are performed, the capillary tube 14 ispositioned, fixed, and bonded at a position at which the distance d1between the end surface 15 a of the optical fiber 15 and the translucentspherical surface 12 b of the partially spherical lens 12 becomes 0.215mm±2 μm. In this manner, the optical collimator 30 is obtained.

Next, another embodiment of the present invention will be described.

As shown in FIG. 10, an optical collimator-use lens component 20includes: a glass thin tube 21 that is 1.80 mm in outer diameter, isφ1.005 mm+0.01/−0 mm in inner diameter of its inner hole 21 b, and is6.0 mm in total length; a partially spherical lens 22 fixed in the innerhole 21 b of the glass thin tube 21 so that an insertion portion 21 ahaving a predetermined length is left; a glass inner thin tube 24inserted into and fastened in the insertion portion 21 a of the glassthin tube 21; and an adhesive 23 made of an epoxy-based ultravioletcuring resin that bonds the partially spherical lens 22 and the glassinner thin tube 24 to the glass thin tube 21. The partially sphericallens 22 is made of optical glass LaSF015 whose refractive index isapproximately uniform, is φ0.98 mm in diameter, and has translucentspherical surfaces 22 b and 22 c, whose centers of curvature areapproximately the same and radiuses of curvature R are each 1.25±0.0015mm, at both ends of its cylindrical portion 22 a. Also, eccentricitybetween the center axis of the outer peripheral surface of the partiallyspherical lens 22 and the center axes of the spherical surfaces is 5 μmor less. The glass inner thin tube 24 is 0.997 mm±0.005 mm in outerdiameter, is 0.68 mm+0.002/−0 mm in inner diameter of its inner hole 24b, and is 3.45 mm in length. The glass inner thin tube 24 is insertedinto and fastened to the insertion portion 21 a of the glass thin tube21 under a state where an end surface 24 a of the glass inner thin tube24 that is at right angles to a tube axis of the glass inner thin tube24 is abutted against the translucent spherical surface 22 b of thepartially spherical lens 22. The axial deviation amount among the centeraxis of the inner hole 21 b of the glass thin tube 21, the optical axisof the partially spherical lens 22, and the center axis of the innerhole 24 b of the glass inner thin tube 24 is 3 μm. Also, the glass thintube 21 and the glass inner thin tube 24 are each made of transparentborosilicate glass that transmits 85% of light, whose wavelength is 350to 500 nm, with a thickness of 1 mm.

FIG. 11 shows an optical collimator 40 that uses the opticalcollimator-use lens component 20. A capillary tube 26, in whose innerhole 26 b an optical fiber 25 has been fixed, is inserted into and fixedin the inner hole 24 b of the glass inner thin tube 24 fixed in theinsertion portion 21 a of the glass thin tube 21. The capillary tube 26is 0.68 mm+0/−0.002 mm in outer diameter and is 5.25 mm in total length.Also, the axial deviation amount between an outer peripheral surface 26a of the capillary tube 26 and the core center of an end surface 25 a ofthe optical fiber 25 is 0.5 μm. When the capillary tube 26 is fixed at aposition at which a distance d2 between the end surface 25 a of theoptical fiber 25 and the spherical surface 22 b of the partiallyspherical lens 22 becomes 0.182 mm±2 μm, emission light has an emissionlight bend of 0.1 that is within a desired range of 0.2° or less.

When the capillary tube 26, to which the optical fiber 25 having theinclined end surface 25 a has been fastened, is fixed to the opticalcollimator-use lens component 20, emission light generates an offset Wfrom the optical axis of the optical fiber 25 only by 95 μm like in thecase shown in FIG. 7. In view of this, insertion loss and return lossmeasurement was performed by aligning offset positions of one pair ofoptical collimator-use lens components 20 arranged so as to oppose eachother while setting a working distance at 20 mm in the manner shown inFIG. 7(B) or (C).

This measurement showed that the optical collimator 40 using the opticalcollimator-use lens component 20 has superior characteristics that donot greatly differ from those of the aforementioned optical collimator30 using the optical collimator-use lens component 10.

Next, a method of assembling the optical collimator-use lens component20 and a method of assembling the optical collimator 40 will bedescribed.

First, as shown in FIG. 12(A), the glass thin tube 21 is prepared whichis 1.005 mm in inner diameter of its inner hole 21 d and is 6.0 mm intotal length. Also, as shown in FIG. 12(B), the glass inner thin tube 24is prepared which is 0.997 mm±0.005 mm in outer diameter, is 0.68mm+0.002/−0 mm in inner diameter of its inner hole 24 b, and is 3.45 mmin length. Further, as shown in FIG. 12(C), the partially spherical lens22 is prepared which is made of optical glass LaSF015 whose refractiveindex is approximately uniform, is φ0.98 mm in diameter, has thetranslucent spherical surfaces 22 b and 22 c whose centers of curvatureare approximately the same and radiuses of curvature R are each1.250±0.0015 mm, at both ends of the cylindrical portion 22 a, and is 5μm or less in eccentricity between the center axis of its outerperipheral surface and the center axes of its spherical surfaces. Stillfurther, as shown in FIG. 12(D), the capillary tube 26 is prepared whichis 0.68 mm+0/−0.002 mm in outer diameter and is 5.25 mm in total length,and the optical fiber 25 is fixed in the inner hole 26 b.

Next, as shown in FIG. 13(B), the glass inner thin tube 24 is insertedinto the inner hole 21 d of the glass thin tube 21 {FIG. 13(A)}, itsright-angled end surface 24 a is positioned at a position at which thelength of the insertion portion 21 a becomes 2.5 mm, and the glass innerthin tube 24 is fastened using the adhesive 23 made of an epoxy-basedultraviolet curing resin. Then, as shown in FIG. 13(C), the partiallyspherical lens 22 is inserted into the inner hole 21 d of the glass thintube 21 and its translucent spherical surface 22 b is abutted againstthe end surface 24 a of the glass inner thin tube 24 and is positioned.Following this, the partially spherical lens 12 is fastened to the innerhole 21 d of the glass thin tube 21 using the adhesive 23. In thismanner, the optical collimator-use lens component 20 is obtained.

Then, as shown in FIG. 13(D), the capillary tube 26, in whose inner hole26 b the optical fiber 25 has been fixed, is inserted into the innerhole 24 b of the glass inner thin tube 24 fixed in the insertion portion21 a of the glass thin tube 21. Then, the capillary tube 26 ispositioned and bonded at a position at which the distance d between theend surface 25 a of the optical fiber 25 and the spherical surface 22 bof the partially spherical lens 22 becomes 0.182 mm±2 μm. In thismanner, the optical collimator 40 is obtained.

It should be noted here that in the embodiment described above, thesplit sleeve is set as a transparent glass tube, although the presentinvention is not limited to this. For instance, the split sleeve may bea plastic tube, a metallic tube having a hole through which it ispossible to observe the distance between the end surface of the opticalfiber and the spherical surface of the partially spherical lens, or thelike.

The insertion loss of the optical collimator described above wasmeasured in a manner described below. That is, two optical collimatorswere produced and prepared, an optical fiber was connected to a laserdiode stabilized light source whose wavelength is 1,550 nm, and one ofthe optical collimators was connected to this optical fiber by means ofa fusion splice. Then, this optical collimator was fixed to a five-axisoptical stage having two rotational axes orthogonal to XYZ spatial axes.Next, the other of the optical collimators was fixed to an optical baseand a tip end of an optical fiber that is a pigtail of the opticalcollimator was connected to a power meter. Following this, an imagingrelation between the two optical collimators was obtained throughalignment using the five-axis stage, and a light reception quantity wasmeasured using the power meter under this state. Then, a light receptionquantity measurement value obtained in advance by directly connectingthe stabilized light source and the power meter to each other through anoptical fiber was subtracted from the light reception quantity measuredin the manner described above, thereby calculating the insertion loss.Also, the return loss of the optical collimator described above wasmeasured in a manner described below. That is, an optical fiber having asufficient length (10 mm or more) was connected to an OTDR (optical timedomain reflect meter). Then, the optical collimator was fixed to a tipend of the optical fiber by means of a fusion splice and the intensityof reflection light was measured, thereby measuring the return loss.

1. An optical collimator-use lens component comprising: a thin tubewherein the thin tube is made of a transparent body with which thedistance between the end surface of an optical fiber and the translucentspherical surface of a partially spherical lens can be measured from theoutside; the partially spherical lens that is fixed in an inner hole ofthe thin tube so that an insertion portion having a predetermined lengthis left, is made of glass whose refractive index is approximatelyuniform, and has translucent spherical surfaces, whose centers ofcurvature are approximately the same, at both ends of a cylindricalportion of the partially spherical lens; and an adhesive that bonds thepartially spherical lens to the thin tube, wherein an axial deviationamount between a center axis of the thin tube and an optical axis of thepartially spherical lens is 5 μm or less, and when a capillary tube, inwhose inner hole an optical fiber has been fixed and whose axialdeviation amount between an outer peripheral surface of the capillarytube and a core center of an end surface of the optical fiber is 1.5 μmor less, is inserted into the insertion portion of the thin tube and theend surface of the optical fiber is fixed at a position at which adistance of the end surface to a focal point position of the partiallyspherical lens becomes ±40 μm or less, emission light has an emissionlight bend of 0.2° or less with respect to the center axis of the thintube.
 2. An optical collimator-use lens component according to claim 1,wherein the partially spherical lens is 1.7 or more in refractive index.3. An optical collimator-use lens component according to claim 1,wherein the distance between the end surface of the optical fiber andthe translucent spherical surface of the partially spherical lens is 0.1mm or more.
 4. An optical collimator-use lens component according toclaim 1, wherein a material of the thin tube comprises one of glass andcrystallized glass.
 5. An optical collimator-use lens componentaccording to claim 1, wherein the thin tube comprises a split sleeve. 6.An optical collimator-use lens component according to claim 1, whereinthe adhesive comprises one of an epoxy-based resin and a low meltingpoint glass frit mixed with a filler made of at least one materialselected from the group consisting of ceramics, glass, and metals. 7.The optical collimator-use lens component according to claim 1, whereinan inner thin tube having an inner hole with a predetermined innerdiameter is inserted into and arranged in the insertion portion of thethin tube, and is bonded and fixed in the insertion portion under astate where an end surface of the inner thin tube that is at rightangles to a tube axis of the inner thin tube with predetermined accuracyis abutted against the translucent spherical surface of the partiallyspherical lens.
 8. An optical collimator-use lens component according toclaim 7, wherein at least one of the thin tube and the inner thin tubeis made of transparent glass that transmits 50% or more of light, whosewavelength is 350 to 500 nm, with a thickness of 1 mm.
 9. A method ofassembling an optical collimator-use lens component including a thintube, a partially spherical lens that has been fixed in an inner hole ofthe thin tube so that an insertion portion having a predetermined lengthis left, is made of glass whose refractive index is approximatelyuniform, and has translucent spherical surfaces, whose centers ofcurvature are approximately the same, at both ends of a cylindricalportion of the partially spherical lens, and an adhesive that bonds thepartially spherical lens to the thin tube, the optical collimator-uselens component assembling method comprising: inserting an inner thintube having an inner hole with a predetermined inner diameter into theinner hole of the thin tube and fixing the inner thin tube under a statewhere an end surface of the inner thin tube that is at right angles to atube axis of the inner thin tube with predetermined accuracy exists at apredetermined position; positioning the partially spherical lens byinserting the partially spherical lens into the inner hole of the thintube so as to be abutted against the end surface of the inner thin tube;and bonding and fixing the partially spherical lens in the thin tube.10. An optical collimator-use lens component assembling method accordingto claim 9, further comprising removing the inner thin tube from theinside of the thin tube one of before and after the partially sphericallens is bonded and fixed in the thin tube.
 11. An optical collimatorcomprising a lens component and a capillary tube into whose inner holean optical fiber has been fixed, wherein: the lens component includes: athin tube wherein the thin tube is made of a transparent body with whichthe distance between the end surface of the optical fiber and thetranslucent spherical surface of a partially spherical lens can bemeasured from the outside; the partially spherical lens that is fixed inan inner hole of the thin tube so that an insertion portion having apredetermined length is left, is made of glass whose refractive index isapproximately uniform, and has translucent spherical surfaces, whosecenters of curvature are approximately the same, at both ends of acylindrical portion of the partially spherical lens; and an adhesivethat bonds the partially spherical lens to the thin tube, an axialdeviation amount between a center axis of the thin tube and an opticalaxis of the partially spherical lens being 5 μm or less; an axialdeviation amount between an outer peripheral surface of the capillarytube and a core center of an end surface of the optical fiber is 1.5 μmor less; and the capillary tube is inserted into the insertion portionof the thin tube of the lens component and is fixed at a position atwhich a distance of the end surface of the optical fiber to a focalpoint position of the partially spherical lens becomes ±40 μm or less.12. An optical collimator according to claim 11, wherein the partiallyspherical lens is 1.7 or more in refractive index.
 13. An opticalcollimator according to claim 11, wherein the distance between the endsurface of the optical fiber and the translucent spherical surface ofthe partially spherical lens is 0.1 mm or more.
 14. An opticalcollimator according to claim 11, wherein a material of the thin tubecomprises one of glass and crystallized glass.
 15. An optical collimatoraccording to claim 11, wherein the thin tube comprises a split sleeve.16. An optical collimator according to claim 11, wherein the adhesivecomprises one of an epoxy-based resin and a low melting point glass fritmixed with a filler made of at least one material selected from thegroup consisting of ceramics, glass, and metals.
 17. The opticalcollimator according to claim 11, wherein an inner thin tube having aninner hole with a predetermined inner diameter is inserted into andarranged in the insertion portion of the thin tube, and is bonded andfixed in the insertion portion under a state where an end surface of theinner thin tube that is at right angles to a tube axis of the inner thintube with predetermined accuracy is abutted against the translucentspherical surface of the partially spherical lens.
 18. A method ofassembling an optical collimator including a lens component and acapillary tube into whose inner hole an optical fiber has been fixed,the lens component including: a thin tube wherein the thin tube isformed using a transparent body with which the distance between the endsurface of the optical fiber and the translucent spherical surface ofthe partially spherical lens can be measured from the outside, and thepositioning is performed while the distance between the end surface ofthe optical fiber and the translucent spherical surface of the partiallyspherical lens is measured from the outside; the partially sphericallens that is fixed in an inner hole of the thin tube so that aninsertion portion having a predetermined length is left, is made ofglass whose refractive index is approximately uniform, and hastranslucent spherical surfaces, whose centers of curvature areapproximately the same, at both ends of a cylindrical portion of thepartially spherical lens; and an adhesive that bonds the partiallyspherical lens to the thin tube, an axial deviation amount between acenter axis of the thin tube and an optical axis of the partiallyspherical lens being 5 μm or less, an axial deviation amount between anouter peripheral surface of the capillary tube and a core center of anend surface of the optical fiber being 1.5 μm or less, and the capillarytube being inserted into the insertion portion of the thin tube of thelens component and being fixed at a position at which a distance of theend surface of the optical fiber to a focal point position of thepartially spherical lens becomes ±40 μm or less, the optical collimatorassembling method comprising: positioning, at the time of the fixationat the position, the capillary tube by measuring a distance between theend surface of the optical fiber and the translucent spherical surfaceof the partially spherical lens from the outside.
 19. An opticalcollimator assembling method according to claim 18, wherein at least oneof the thin tube and an inner thin tube is made of transparent glassthat transmits 50% or more of light, whose wavelength is 350 to 500 nm,with a thickness of 1 mm.